Circuit breaker



Jan. 18, 1949. D, DORFMAN ET AL 2,459,629

CIRCUIT BREAKER Filed Aug. 10, 1945 ITNESSES: H W mvENTO J/ W127. Dory/flan and GerQ/BQYJ'FFeese.

i a ATTORNEY Patented Jan. 18, 1949 CIRCUIT BREAKER Hiller D. Dorfman,

Pittsburgh, and Gerald J. Freese, East McKeesport, Pa.,

assignors to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application August 10, 1945, Serial N0. 610,104

10 Claims.

This invention relates to electric circuit interrupters, and more particularly to bimetallically controlled circuit breakers.

One object of the invention is to provide a circult breaker having a thermal trip device with novel means for preventing tripping of the breaker in response to mechanical shocks.

Another object is to provide a circuit breaker with a novel shock-proof tripping device.

Another object of the invention is to provide a circuit breaker with a novel bimetallic trip element which is supported at both ends to prevent tripping of the breaker in response to sudden shocks. 7

The novel features that are considered characteristic of the invention are set forth in particular in the appended claims. self, however, both as to structure and operation, together with additional objects and advantages thereof, will be best understood from the following detailed description of one embodiment thereof when read in conjunction with the accompanying drawing, in which: a

Fig. 1 is a longitudinal sectional view of a circuit breaker embodying the principles of the invention, one of the supporting plates for the breaker mechanism being removed to show the mechanism in elevation, the breaker mechanism being shown in the closed position;

Fig. 2. is a sectional view similar to Fig. l but showing the parts in the tripped open position.

The circuit breaker is illustrated on the drawings as being com'ined in a casing of insulating material, preferably of a molded insulating material or the like. portions including a base portion 2, and a cover portion 4, secured together as by bolts 6 passing through aligned openings provided in each casing portion. In the particular form of casing illustrated, bolts 6 may be provided only in diagonally opposite corners of the casing, with the aligned bores 8 provided in the other pair of diagonally opposite corners of the casing being left for the reception of mounting bolts or the like.

The circuit breaker mechanism is for the most part supported between a pair ofspacedsupporting plates I ll of like configuration, Within the insulating casing. Supporting plates l0 (only one of which is shown) are disposed adjacent the side walls of the casing, and each plate is provided with integral extensions ll adapted to project through openings provided in the bottom wall of the casing, as to be riveted over on the outside of the casing as at l5, to secure the supporting plates in operative position in the casing. Sup- The invention it- The casing comprises two half ill purpose is provided with a porting plates ID are also secured together by connecting rivets l2 and I3, to prevent relative movement of the plates. Rivet I2 is located with respectto the plates in the particular position shown in Figs. 1 and 2, for a purpose to be de scribed.

A movable contact bar 22 is adapted to be supported between supporting plates l0, and for this slot 20 for receiving a pivot pin 16 having reduced ends adapted to be received in supporting plates l0. Contact bar 22 is provided with a contact 24 at the outer end thereof, which is preferably of some good are resistant conducting material, such as a silver alloy. Contact 24 on the movable contact bar is adapted to engage a fixed contact 26 of similar material, secured by means of a rivet 28 to the bottom wall of the breaker casing. Rivet 28 also supports, on the exterior of the casing, a terminal strap 30, having a terminal screw 32, by means of which a circuit conductor may be electrically connected with the breaker. Contact bar 22 is biased by a spring 34 engaging a projection 38 on the inner end thereof, to urge contact bar 22 in a direction to cause the bottom of slot 20 to engage pivot pin l6. As illustrated in the drawings, biasing spring 34 is adapted to be received in a depression 35 provided in the bottom wall of the casing.

A carrier bar 40 is also supported between supporting plates ID, by means of a pivot pin H, having reduced ends received in openings provided in supporting plates l0. Normally carrier bar 40 is maintained against clockwise movement about pivot pin M, by engagement of a nose 42 thereof beneath a latch 44. A bimetal element 68 carries the latch 44, and is adapted to be actuated to release the carrier bar and effect automatic opening of the contacts, in a manner to be hereinaiter described. The actuating mechanism for movable contact bar 22 is connected between carrier 40 and contact bar 22, and comprises a. pair of toggle links 41 (only one being shown) pivotally mounted on carrier bar 40 as by a pivot pin 48. A second pair of toggle links 52 (only one being shown) is pivotally mounted on contact bar 22 as by a pivot pin 54, and these toggle links are pivotally connected with toggle links 41, by a knee pivot pin 50.

In order to actuate the toggle mechanism cor n prising links 41 and 52, a pair of actuating levers 56 (only one being shown) have their inner ends pivotally received in the rounded inner ends ofsubstantially V-shaped notches 58, provided in the upper side of each supporting plate I0. Ac-

tuat ing levers 56 are rigidly connected together by a connecting r et 62, and the inner ends of these levers are prevented from moving laterally out of notches 56 by means of plates 60 (only one being shown) which are secured to supporting plates H) at the inner ends of notches 58. A pair of overcenter tension springs 64 (only one being shown) are connected between knee pivot pin 50 of the toggle levers and connecting rivet 62 of the actuating levers, for the purpose of actuating the toggle levers and consequently contact bar 22 with a snap action, upon pivotal movement of actuating levers 56.

In the operation of the parts of the circuit breaker thus far described, it will be observed that in the closed circuit position shown in Fig. l, toggle levers 41 and 52 are held at an extended position slightly beyond the dead-center position, where overcenter spring 64 holds a spacing washer 5| disposed between the toggle links on the knee pivot pin 56 of the toggle in engagement with the adjacent edge of angular portion 65 of carrier 40. Now assuming it is desired to open the breaker contacts, actuating levers 56 are pivotally moved to the left, or in a counterclockwise direction, to carry the upper ends of overcenter springs 64 past toggle pivot 48. As soon as this occurs, the spring is effective to cause collapse of the toggle levers to the left, and thereby separate contact 24 from fixed contact 26. It will be noted that in the closed circuit position,

the toggle is effective to stress spring 34 so that pivot pin I6 is located at an intermediate position in slot 26. Spring 34 thus serves to determine the pressure with which contact 24 engages contact 26, because this spring in the closed circuit position tends to rotate contact 24 into engagement with contact 26 about pivot pin 54. Accordingly, when the circuit is opened by collapse of the toggle, as described above, biasing spring 34 moves the adjacent end of contact bar 22 relative to pivot pin l6, until the bottom of slot 20 engages the pivot pin, and thereafter movement of the contact bar 22 is purely pivotal relative to pivot pin l6, the opening movement of the contact bar 22 being arrested by engagement with the carrier lever 46. In closing the circuit,

the reverse operation takes place, that is, actuating levers 56 are pivotally moved back to the position shown in Fig. 1 to straighten the toggle,

thus causing pivotal movement of contact bar 22 in clockwise direction relative to pivot pin l6 until contact 24 engages fixed contact 26, where upon this pivotal movement ceases, and the remaining movement of toggle levers 41 and 52 to the position shown in Fig. 1 results in stressing biasing spring 34 by substantially pivotal movement of the contact bar about the point of engagement thereof with fixed contact 26, in a counterclockwise direction.

The bimetal element 66 is formed from a bimetal strip and is constructed in a, well known manner of a pair of laminations having, respectively, high vand low thermal coefiicients of expansion, with the strip arranged so that the lamination having the higher coeiiicient of expansioniies adjacent the nose 42 of the carrier lever 46. The bimetal element 66 has the lower end thereof bent at an angle to form a foot 61 with-"a radius between the foot and the substantially vertical portion thereof. The foot 61 .of the bimetal element is secured to the bottom wall of the breaker casing by a rivet 13 which also serves to secure a terminal strip M to the outside of the casing. The terminal strip is prois heated, the leg 66 which carries the latch 44' will deflect toward the left and the leg 69 will deflect toward the right a proportionate amount and will, at all times, remain in contact with the abutment 16. In this manner, the bimetal element is prevented from moving in tripping direction as a result of mechanical shocks or jarring forces. The main portion 66 of the bimetal element may be made somewhat longer in proportion to the length of the leg 69 in which event the deflection of the leg 66 will be proportionately greater than the deflection of the leg 66 and the leg 66 will be pressed against the stop screw 10 with increasing pressure as the heating of the bimetal increases, thus increasing the resistance to shocks. The same result may be obtained by attaching the shunt conductor 18 to the leg 69 at a point closer to the curved portion 68 so that the leg 69 will be heated to a lesser degree and, hence, will deflect proportionately less than the main portion 66 of the bimetal for a given amount of heating in response to overload currents traversing the bimetal ele ment.

The electric circuit through the circuit breaker may now be traced from terminal strip 14 through rivet 13, bimetal strip 66 and a flexible shunt [6 connecting a midpoint of the leg 69 of bimetal strip 66 to contact bar 22, to contact 24 and contact 26 when the parts are in the closed circuit position, thence by rivet 26 to terminal strip 30. Although bimetal strip 66 is thus at least partly electrically connected in series in the circuit through the breaker so as to be heated directly by currents in excess of a predetermined value to cause deflection thereof, it is obvious that it may not be in the electric circuit at all but may be heated by a separate heaterconnected in series in the circuit, in a manner well known in the art. It will be apparent that when bimetal strip 66 is heated and the upper end thereof defiects to the left, as viewed in Fig. 1, it will move latch 44 in the same direction until the latch 44 escapes from nose 42 of carrier 40, to thus permit overcenter spring 64 to bodily raise the toggle levers while rotating carrier 46 in a clockwise direction about its pivot H, to thus move contact bar 22 to open circuit position, substantially in the manner previously described.

In order to manually actuate the circuit breaker contacts, and to reset the mechanism following an automatic circuit interrupting operation in the manner disclosed above, an actuating handle is provided for actuating levers 56, with this handle 85 being of an insulating material, preferably a molded insulating material, and comprising a generally arcuate shaped base portion adapted to lie closely adjacent the arcuate inner surface 82 of the top wall of the casing. The handle structure further includes a handle portion 85 adapted to project through an opening 81 in the casing cover, for manual manipulation at the exterior of the casing. The'underside of base portion 86 of the handle structure is provided with a groove for receiving connecting rivet 62 of the actuating levers, and each side of base portion III is provided with a recess ll of substantially the same shape and form as the outer ends of actuating levers 56, to closely frictionally receive the outer ends of these levers. The

handle structure is prevented from becoming disengaged from actuating levers 56, by engagement of the base portion 80 thereof with the inner surface of the top wall of the casing. Moreover, base portion 80 of the handle structure acts to substantially close, opening 81 in the casing at all positions of the handle. Base portion 80 of the handle structure is provided at one end with spaced depending integral flanges 86 (only one of which is shown), for the purpose of supporting between the outer ends thereof a reset pin 88 suitably mounted in apertures provided in flanges 86.

Now assuming that an automatic circuit interrupting operation has occurred by reason of deflection of bimetal strip 66 to release carrier 40 which has rotated in a clockwise direction about pivot ll to a position wherein portion 65 thereof engages the stop pin l2, connected between supporting plates ill, by then moving handle portion 85 to the left, which pivots actuating levers 56 in nism therefor, thermally responsive means nora counterclockwise direction, engagement of reset 7 pin 88 on the handle structure with projection 89 on carrier 40, will cause movement of the carrier with the handle structure and actuating levers back to the position where the nose 42 thereof may re-engage beneath latch 44. This resets carrier 40 to the position shown in Fig. 1, and the circuit breaker may then be closed by moving handle portion 85 back to the position shown in Fig. 1. Obviously, actuating levers 56 are moved whenever handle portion 85 is manually moved, so that the breaker contacts may be manually opened and closed by operation of handle portion 85 to cause appropriate movement of actuating levers 56 to operate the breaker contacts in the manner previously described.

From the foregoing description, it will be apparent that there is provided a circuit breaker of simple, rugged construction wherein the thermal trip element is rigidly supported at both ends to prevent tripping movement thereof in response to mechanical shocks or sudden jarring forces.

Having described a preferred embodiment of the invention in accordance with the patent statutes, it is to be understood that various changes and modifications may be made therein without departing from some of the essential features of the invention. It is, therefore, desired that the language of the appended claims be given as reasonably broad interpretation as the prior art permits.

We claim as our invention:

1. In a circuit breaker comprising relatively movable contacts and releasable operating mechanism for said contacts, a U-shaped bimetal element having legs of unequal length normally restraining said operating mechanism against movement, said bimetal element having one leg rigidly secured to a fixed member, and a fixed abutment cooperating with the other leg of said bimetal element to prevent movement of said bimetal in releasing direction in response to sudden shocks or jarring forces.

2. In a circuit breaker comprising relatively movable contacts and releasable operating mechanism for said contacts, a U-shaped bimetal element normally restraining said operating mechanism against movement, said bimetal element having one end rigidly secured to a fixed mally restraining said operating mechanism against operation and operable when heated in response to overload currents to release said operating mechanism, saidthermally responsive means comprising a bimetallic strip having one end formed into a U-shape with legs of unequal length, means rigidly mounting the longer leg of said bimetallic strip, and means rigidly supporting the shorter leg of said bimetallic strip to oppose releasing movement of said thermally responsive means as a result of mechanical shocks or jarring forces.

4.. In a circuit breaker comprising relatively movable contacts and a releasable operating mechanism therefor, a bimetal trip element return bent about atransverse axis parallel to its faces to form a loop having legs of unequal length, latch means on one leg of said bimetal element at a point adjacent the loop for normally restraining said operating mechanism in operative position, said bimetal element having the high expansion side on the outside and operable when heated a predetermined amount in response to overload currents to deflect said legs toward each other to release said operating mechanism, a mounting foot formed on one leg of said bimetal element, means rigidly securing said foot to a fixed member, means rigidly supporting the othe leg of said bimetal element opposite said latch to prevent tripping movement of said ele-- ment in response to sudden shocks, said other leg of the bimetal element remaining in contact with said support means during tripping operation of said bimetal and also while said bimetal cools.

5. In a, circuit breaker comprising separable contacts and releasable operating means therefor, a U-shaped bimetal element normally restraining said operating mechanism, said bimetal element having legs of unequal length, said himetal element being connected in the circuit of the breaker so that the longer leg and at least a portion of the shorter leg are heated by the current of the circuit, means fixedly mounting the longer leg of said bimetal element, a fixed abutment cooperating with the shorter leg of said bimetal element to oppose movement of said bimetal in releasing direction in response to sudden shocks, the legs of said bimetal element being proportioned so that as the bimetal deflects the shorter leg thereof remains at all times in contact with said support means.

6. In a circuit breaker comprising relatively movable contacts and releasable operating mech-- anism for said contacts, a U-shaped bimetal element disposed to be heated by the current of the circuit, said bimetal element having legs of unequal length disposed to deflect toward each other, said bimetal element having the high expansion side on the outside and operable when heated a predetermined amount to effect release of said operating mechanism, means fixedly mounting the long leg of said bimetal element, and means rigidly supporting the short leg of said bimetal element, the relative length of said legs being such that as said legs deflect toward each other, said short leg remains in contact with said support means to oppose false tripping of said breaker as a result of sudden shocks.

7. In a circuit breaker comprising separable contacts and operating mechanism releasable to effect automatic separation of said contacts, trip means normally restraining said operating mechanism and operable to release said operating mechanism, said trip means comprising a thermally responsive element formed from a bimetallic strip having an angular bent portion for rigidly mounting said thermally responsive element and having a single reverse curvature forming portions of unequal length with the high expansion side on the outside of said curvature, said portions being disposed to deflect when heated toward each other, and means for rigidly supporting the free end of said thermally responsive element to oppose tripping movement of said element in response to mechanical shocks or jarring forces.

8. In a circuit breaker comprising releasable operating mechanism for effecting automatic opening of said breaker, a bimetal element having a reverse bend about a transverse axis parallel to its faces to form a loop, said bimetal element having the high expansion side on the outside of said loop, means actuated by one leg of said bimetal at a point adjacent said loop for initiating release of said operating mechanism, means rigidly securing said one leg to a fixed member, and a fixed abutment cooperating with the other leg of said bimetal element toprevent movement of said bimetal element in releasing direction in response to shocks.

9. In a circuit breaker comprising releasable operating mechanism for eifecting automatic opening of said breaker, a bimetal clement having a reverse bend about a transverse axis parallel to its faces to form a loop, said bimetal element having the high expansion side on the outside of said loop, latch means on one leg of said bimetal adjacent said loop for restraining said operating mechanism, means rigidly securing said one leg to a fixed member, and a fixed abutment disposed at the side of the loop opposite said latch and cooperating with the other leg of said bimetal element to prevent movement of said bimetal element in releasing direction in response to shocks.

10. In a circuit breaker comprising releasable operating mechanism for afiecting automatic opening of said breaker, a bimetal element having a reverse bend about a transverse axis parallel to its faces to form a loop, said bimetal element having the high expansion sid on the outside of said loop, means actuated by one leg of said bimetal element at a point adjacent said loop for initiating releasing of said operating mechanism, said means being movable in releasing direction only when said bimetal element defiects in response to overload currents, means rigidly securing said one legto a fixed member, and a fixed abutmentcooperating with the other leg of said bimetal element to prevent movement of said bimetal element in releasing direction in response to shocks.-

I-IIILER D. DORFMAN. GERALD J. FREESE.

REFERENCES CITED The following references are of record the file of this patent:

UNITED STATES PATENTS Number Maseng June 19, 1945 

